1. Field of the Invention
The present invention relates to a method and apparatus for centering a belt-shaped material such as belt material for tires.
2. Description of the Related Art
In a process of manufacturing tires, a centering apparatus is used to center a belt material before the belt material is wound around a forming drum.
In such a centering apparatus, when a belt material, which has a constant width and is wound around a supply reel in a belt feed section, is fed out, the belt material is further conveyed by a cutting conveyer disposed at the downstream side of the supply reel, i.e., the side in the direction of feeding out the belt material. The conveying direction leading end of the belt material on the cutting conveyor is first cut obliquely by a cutter, and then the belt material is again cut obliquely by the cutter after being conveyed a predetermined distance. Thus, a piece of the belt material having a predetermined length is obtained.
The belt material cut to the predetermined length is fed out of the cutting conveyer, and is conveyed to an applying conveyer disposed at the conveying direction downstream side of the cutting conveyer. A forming drum which is rotatably supported is disposed at the downstream side of the applying conveyor. The belt material conveyed by the applying conveyer is wound onto the outer circumferential surface of the forming drum, which is rotating.
On the forming drum, the leading end and trailing end of the belt material must be joined together such that the cut surfaces of both ends coincide. Further, the widthwise center line of the constant-width portion of the belt member must coincide with the circumferential direction of the forming drum (i.e., the belt material must not meander).
In order to satisfy the above requirements, belt materials have conventionally been centered in accordance with, for example, (1) a method in which the belt material is centered through use of guides having a predetermined guide width without measurement of the overall width of the belt material, or (2) a method in which a cutting conveyer is moved in the widthwise direction of the belt material by a motor-driven mechanism in order to control the position at which the belt material is conveyed from the cutting conveyer to the applying conveyer such that the leading end, the trailing end, and the constant-width portion of the belt material are conveyed to respective predetermined positions (Japanese Patent Application Laid-Open No. 7-195570).
However, method (1), in which the overall width of the belt material is not measured, has the following drawbacks:
(a) When the width of the belt material is larger than the distance between the guides, widthwise end portions of the belt material ride onto the guides, resulting in improper centering of the belt material; PA1 (b) When the width of the belt material is smaller than the distance between the guides, the belt material abuts none of the guides, resulting in improper centering of the belt material, and play is present between the guides and the belt member such that the belt material shifts to the right or left side in the widthwise direction; and PA1 (c) If the leading end and the trailing end of the belt material come out of position relative to each other at the joint portion such that a stepped portion is formed, such a problem cannot be handled. PA1 (d) Since the entire cutting conveyer is moved, the belt material is skewed when it is conveyed from the belt feed section to the cutting conveyer; and PA1 (e) Since the entire cutting conveyer, including the cutter apparatus, must be moved at high speed, a large amount of energy is required.
Method (2) has the following drawbacks:
Moreover, due to cords disposed in the belt material such that they are inclined with respect to the longitudinal direction of the belt material, when the obliquely cut leading and trailing ends of the belt material ride onto the forming drum, the leading end and the trailing end may shift in the widthwise direction. No measures have been employed to cope with such a problem.